I don't have a direct answer for you, but I'll recount my experience with a low tech, low light set up.
I've pasted a link to a pic of the tank, this was quite soon after it was set up.
I just used gravel as a substrate. I used the Flourish range of products for quite some time and while using them I had extremely good results. I did use a product available here in Australia called Dinosaur Dung, which is just a pellet of dried clay with nutrients in it. You put in under the gavel near where you plant the plants. It worked ok but would cloud the water when disturbed during re-planting. The lighting was 2 36W flouro tubes. I am reluctant to use anything other than gravel because of the compaction. Plus when that occurs, you can get oxygen depletion in the substrate leading to sufur dioxide production.
I hope that someone with experience with your situation reads the thread and can offer more positive advice.